Download Failed Error Code: NULL when Scanning QR Code

[HelioZF]

I have followed all the steps to install the app, but when I scan the QR code, I receive the following error message:

Download Failed, error code: NULL.

I have already changed my account to a normal one (not linked with Google), but the error persists. How can I resolve this issue?
Note: My watch is the amazfit balance, i am trying to download the app for the gtr4
Thank you for your assistance!